1. Field of the Invention
In general, the present invention relates to an active-matrix display apparatus employing a light emitting device in each of its pixel circuits and a driving method for driving the display apparatus. In addition, the present invention also relates to electronic instruments each making use of an image display apparatus of this type.
2. Description of the Related Art
In an image display apparatus such as a liquid-crystal display apparatus, a number of pixel circuits are laid out to form a matrix. The image display apparatus displays an image by controlling the transmissivity or reflectivity of incoming light for each pixel circuit in accordance with information of the image to be displayed. The same method as that adopted by the image display apparatus such as the liquid-crystal display apparatus is also adopted in an organic EL (Electro Luminescence) display apparatus which makes use of an organic EL device in each of its pixel circuits. However, the organic EL display apparatus is different from the liquid-crystal display apparatus in that each of the organic EL devices employed in the organic EL display apparatus is a light self-emitting device. Thus, in comparison with the liquid-crystal display apparatus, the organic EL display apparatus offers merits such as a high visibility, no required backlight and a high response speed. In addition, the organic EL display apparatus is different from the liquid-crystal display apparatus in that the luminance level (or the gradation) of light emitted by the light self-emitting device employed in the organic EL display apparatus is controlled by a current flowing through the light self-emitting device whereas the luminance level of light emitted by the light emitting device employed in the liquid-crystal display apparatus is controlled by a voltage applied to the light emitting device. That is to say, the organic EL display apparatus adopts the so-called current control method whereas the liquid-crystal display apparatus adopts the so-called voltage control method. In the following description, the light self-emitting device employed in the organic EL display apparatus is referred to simply as a light emitting device for the sake of convenience.
Similar to the liquid-crystal display apparatus, the organic EL display apparatus adopts a driving method which can be a simple matrix driving method or an active matrix driving method. The simple matrix driving method has a simple structure. However, the simple matrix driving method raises a problem that it is difficult to implement an organic EL display apparatus having a large size and a high definition. For this reason, the active matrix driving method is being developed extensively at the present day. In accordance with the active matrix driving method, a current flowing through the light emitting device employed in each pixel circuit of the organic EL display apparatus is controlled by making use of an active device such as a TFT (Thin Film Transistor) also employed in the pixel circuit. For more information on the organic EL display apparatus and the active matrix driving method adopted, refer to Japanese Patent Laid-open Nos. 2003-255856, 2003-271095, 2004-133240, 2004-029791, 2004-093682, and 2006-215213